The present invention relates to a method for recycling the resin mold comprising adding rubber-like material having compatibility with a thermoplastic resin which is the main component of said resin mold as a recycle aid agent when discarded resin mold is recycled by heating and melting.
Recycling the resin mold containing thermoplastic resin as a main component comprises collecting waste resin mold, washing and shattering said waste resin mold, pelletizing said shattered waste resin mold, and re-molding said resulting pellet. Said method for recycling the resin mold is called xe2x80x9cmaterial recyclexe2x80x9d and during said process, said thermoplastic resin may be decomposed by heating in the pelletizing process, the re-mold process and the like. By heating repeatedly in said processes, molecular bond in said thermoplastic resin may be cut and the molecular weight of said thermoplastic resin may lower and in the case of the thermoplastic resin in which a rubber like component (rubber component, rubber like material, rubber like polymer, rubber like copolymer, graft copolymer) is added to improve the physical properties such as impact strength, elongation, and the like, said thermoplastic resin is such as ABS resin, HIPS resin, modified PPE resin and the like, said rubber component is oxidized and degradized (gellation) resulting in degradation of impact strength.
Further many kinds of additives are combined in said thermoplastic resin and some of said additives have no compatibility with said thermoplastic resin. For instance, the pigment or the dyestuff such as titanium oxide, carbon black, iron oxide, and the like added for coloring of said thermoplastic resin, the inorganic material (inorganic filler) such as glass fiber (GF), glass beads (GB), carbon fiber (CF), talc, calcium carbonate, and the like added for increasing the rigidity of said thermoplastic resin have poor compatibility with said thermoplastic resin. When said materials are contained in said thermoplastic resin in a large amount, the physical properties of said thermoplastic resin may degrade by repeating recycling.
For instance, the waste resin mold collected may be assorted by each kind of resin and further each color of resin and then washed enough, shattered, adjusted color, and pelletized. In case where a desired amount of the virgin thermoplastic resin is added to said pelletized recycled thermoplastic resin to adjust color or the contained amount of impurities, further pigment or dyestuff may be added to said pelletized recycled thermoplastic resin or said virgin thermoplastic resin and as a result, the containined amount of said pigment or dyestuff in the blended resin of said recycled resin and said virgin resin increase resulting in degradation of impact strength.
In said material recycle system (WO9738838), it is described that said collected waste resin mold is shattered without assorting and pelletized and the resulting mold having a mixed color is coated with a paint containing a thermoplastic resin as a main component having compatibility with said resin of said mold to adjust color.
In the case of recycle of closed loop in which the recycle of said resin mold is performed repeatedly, the paint film coated on the surface of said resin mold melts and disperses in said thermoplastic resin which is the main component of said resin mold and dissolve in said thermoplastic resin since the main component of said paint film is a thermoplastic resin.
When said paint film melts and dissolves in said thermoplastic resin, the additives such as the pigment, the dyestuff and the like contained in said paint film disperses in said thermoplastic resin and as a result, the content of said pigment, dyestuff, and the like increases. Said pigment and dyestuff in said paint film have mostly poor compatibility with said thermoplastic resin, resulting in degradation of the physical properties such as impact strength, fluidity, and the like.
Content of the pigment and the dyestuff in the colored resin mold (virgin resin mold) is about 0 to 1.5% by weight while content of the pigment and the dyestuff in the dried colored paint film is about 30 to 70% by weight so that the pigment and the dyestuff content of said paint film is larger than that of said thermoplastic resin.
For instance, assuming that a paint film containing 60% by weight of the pigment and the dyestuff is formed on one side of a panel shaped mold whose thickness is 3 mm, the length and the width are 500 mm respectively. In a case where the virgin resin mold contains 0.3% by weight of the pigment and the dyestuff, the product of the weight of the virgin resin moldxc3x97the pigment and dyestuff content is 500 mmxc3x97500 mmxc3x973 mmxc3x971 (specific gravity)xc3x970.3% by weight=2,25xc3x97105.
In the case of the dried paint film, the product is 500 mmxc3x97500 mmxc3x970.015 mm (in the case of one side coating)xc3x971 (specific gravity)xc3x9760 Wt %=2.25xc3x97105. As above described, in the case of recycle of the coated resin mold, the pigment and dye stuff content may become twice by as much as that of one time recycle and the pigment and the dyestuff content in said thermoplastic resin which is the main component of said resin mold increases as above described, resulting in the degradation of the physical properties of the recycled resin mold since said pigment and said dyestuff have poor compatibility with said thermoplastic resin respectively (compare Table 1 with Table 2).
A paint 0001 containing styrene modified acrylic resin having the compatibility with ABS resin of said resin mold (whose formulation is shown in Table 3) was coated on a resin mold produced by the injection mold of ABS resin (Styrac 191F, Asahi Kasei Corporation.) and said coated resin mold was shattered with the paint film and pelletized to re-mold. Physical properties after said process was repeated three times are shown in Table 1. As a comparison, said process consisting of shattering, pelletizing, and re-mold of said resin mold was repeated three times without coating said paint and the result was shown in Table 2.
Referring to Tables 1 and 2, it is recognized that IZOD impact strength of said recycled resin mold with paint coating degrades comparing with that of said recycled resin mold without paint coating. The reason why impact strength of said recycled resin mold degrades seems to be the effects of the pigment and the dyestuff in said paint film.
The physical properties degrade both in a case where said resin mold is coated with paint or in a case where said resin mold is not coated with paint. Said degradation of the physical properties seems to be caused by the degradation of the rubber component in ABS resin (AnSt-g-PBD).
In the case of the resin containing the same rubber component as the rubber component of ABS resin, such as HIPS, modified PPE, and the like, said rubber component degrades by repeated heating to melt, resulting in the degradation of impact strength of said thermoplastic resin (refer to Reference 3 and others).
As above described, the reasons of the degradation of impact strength by the repeated recycling process in the xe2x80x9cmaterial recyclexe2x80x9d are as follows;
(1) In the case of the recycle of the coated resin mold, the pigment and the dyestuff in the paint film migrate in said thermoplastic resin which is the main component of said resin mold during the heating and melting process to increase the content of the pigment and dyestuff having poor compatibility with said thermoplastic resin which is the main component of said resin mold, resulting in the degradation of impact strength.
(2) Even in the case of the recycle of the uncoated resin mold the molecular weight of said organic thermoplastic resin which is the main component of said resin mold becomes lower by repeated heating and melting in recycle and when a rubber component is added in said thermoplastic resin to improve impact strength, said rubber component degrades by heating and oxidation, resulting in the degradation of impact strength.
The following methods for recovering the physical properties degraded by the recycle have been provided.
In Tokkaihei 5-4228, it is described that a recycle aid agent consisting of two or more kinds of polymer components having different properties but compatibility respectively is added to one or more kinds of waste plastic wherein one polymer component disperses in the other polymer component in particle sizes between 0.0001 and 10 xcexcm and each polymer component bonds chemically together to form a polyphase structure to recover impact resistance, bending elasticity, appearance and the like.
In Tokkaihei 5-92430, it is described that the coated automobile parts made of olefin resin is shattered and olefin resin, olefin elastomer and diene polymer having OH group at its end or hydrogenated diene polymer is blended in said shattered automobile parts to improve impact strength.
Nevertheless in this case it is feared that when the recycled resin mold is coated with a paint, the resulting paint film has poor adhesiveness with said recycled resin mold in a case where some kind of said material is added in the waste plastic.
In Tokkaihei 6-298991, it is described that material wherein rubber like polymer is copolymerized or graft copolymerized to said materials is added in the waste plastic for recycle. Nevertheless, in this case, it is feared that the resulting paint film has poor adhesiveness with the recycled resin mold in a case where some kinds of said material is added in the waste plastic.
In Tokkaihei 8-245756, it is described that epoxydized diene polymer (partially hydrogenated) is added in the recycled material to recover impact strength. Nevertheless there is no disclosure about compatibility with said thermoplastic resin which is the main component of said resin mold and no disclosure about graft copolymerization or copomerization of monomer(s) constituting said thermoplastic resin which is the main component of said resin mold to give compatibility with said thermoplastic resin which is the main component of said resin mold.
Further, no data about the degradation of impact strength by recycle is indicated and repeated recycling is also not described, and there are no disclosure about the cause of the degradation of the physical properties of the resin mold by recycle in this publication.
Still further this publication illustrates the rubber components used to recover impact strength but only refers to adding a rubber component to recover impact strength according to detailed description and examples.
In Tokkaihei 7-228722, it is indicated that degraded impact strength is recovered by shattering said resin mold coated with a paint having no compatibility with polymer alloy, of a modified PPE resin and a polyamide resin, which is a thermoplastic resin as the main component of said resin mold, and adding a hydrogenerated styrenebutadiene block polymer in said shattered resin mold, and contaminating the paint film having no compatibility with the recycle. In this case it is feared that when said hydrogenated styrene butadiene block copolymer content increases, the paint film has poor adhesiveness.
Further there are no detailed description of the rubber component.
In Tokkaihei 10-204207, Tokkaihei 10-168357, Tokkaihei 10-168343 etc., there is description of adding the virgin material to the recycled material, but to recover the degraded physical properties by adding the virgin material, a lot of virgin material is necessary, and so this method is not economical and can not attain a high recycle ratio.
An object of the present invention is, in a method for recycling the resin mold comprising mainly of the thermoplastic resin, to solve the problems about degradations of impact strength and non-flammability and the recovery of impact strength and non-flammability without decreasing the adhesiveness of the paint film by adding the recycle aid agent.
Accordingly, the inventor paid attention to a technical idea of the present invention wherein a rubber-like material having compatibility with thermoplastic resin, which is the main component of a resin mold and so even if said rubber-like material is mixed in said thermoplastic resin, the resulting mixture can be molded. Said rubber-like material having properties to improve impact strength, is added as a recycle aid agent in said thermoplastic resin, and said non flammable material is added in said thermoplastic resin. Thus the inventor has attained the object of the present invention to recover impact strength and non flammability and maintain the sufficient adhesiveness of the paint film.
The present invention (the first invention according to claim 1) relates to a method for recycling the resin mold comprising adding rubber-like material having compatibility with a thermoplastic resin which is the main component of said resin mold as a recycle aid agent when discarded resin mold is recycled by heating and melting.
According to the invention (the second invention according to claim 2) of a method for recycling the resin mold in accordance with claim 1 wherein said resin mold is coated with a paint and said resin mold is melted without separating the paint film.
According to the invention (the third invention according to claim 3) of a method for recycling the resin mold in accordance with claim 1 or 2 wherein glass temperature of said rubber-like material determined by the scanning differential thermal analysis is lower than 200xc2x0 C.
According to the invention (the fourth invention according to claim 4) of A method for recycling the resin mold in accordance with claims 1 to 3 wherein the particle size of said rubber-like material added and dispersed in the melted resin mold containing said thermoplastic resin as the main component is in the range between 0.05 xcexcm to 50 xcexcm and the aspect ratio is larger than 0.1.
According to the invention (the fifth invention according to claim 5) of a method for recycling the resin mold in accordance with claims 1 to 4 wherein said rubber-like material consists of a rubber component and the same or similar resin structure as (to) said thermoplastic resin which is the main component of said resin mold.
According to the invention (the sixth invention according to claim 6) of a method for recycling the resin mold in accordance with claim 5 wherein said rubber component is butadiene group rubber.
According to the invention (the seventh invention according to claim 7) of a method for recycling the resin mold in accordance with claim 5 wherein said rubber component is olefine group rubber.
According to the invention (the eighth invention according to claim 8) of a method for recycling the resin mold in accordance with claim 7 wherein Mooney viscosity ML1+4, 100xc2x0 C. of said olefine group rubber is in the range between 5 to 150.
According to the invention (the ninth invention according to claim 9) of a method for recycling the resin mold in accordance with claim 7 or 8 wherein said olefine group rubber is ethylene-propylene group rubber.
According to the invention (the tenth invention according to claim 10) of a method for recycling the resin mold in accordance with claim 9 wherein said ethylene-propylene group rubber is ethylene-propylene-nonconjugated diene compound copolymer rubber.
According to the invention (the eleventh invention according to claim 11) of a method for recycling the resin mold in accordance with claim 10 wherein said coporimerization ratio of said ethylene-propylene-nonconjugated diene compound is 0.2 to 0.8/0.2 to 0.8/0xcx9c0.05.
According to the invention (the twelfth invention according to claim 12) of a method for recycling the resin mold in accordance with claim 5 wherein said rubber component is an acrylic rubber.
According to the invention (the thirteenth invention according to claim 13) of a method for recycling the resin mold in accordance with claims 1 to 12 wherein said rubber-like material is a mixture of two or more kinds of said rubber-like materials.
According to the invention (the fourteenth invention according to claim 14) of a method for recycling the resin mold in accordance with claims 1 to 13 wherein said rubber-like material is a mixture of two or more of the same or different kinds of said rubber-like material having a different particle size respectively.
According to the invention (the fifteenth invention according to claim 15) of a method for recycling the resin mold in accordance with claims 6 to 14 wherein said thermoplastic resin which is the main component of said resin mold is polystyrene group resin, HIPS resin, acrylonitrile-styrene group copolymer resin, ABS group resin, poly phenylene ether group resin, modified polyphenylene ether group resin, or polymer blend or polymer alloy containing one or more kinds of said thermoplastic resin(s) as the main component and said rubber-like material has the same or similar resin structure as (to) said thermoplastic resin wherein said resin structure is the polymer chain of styrene group monomer or the copolymer chain of styrene group monomer or nitrile group monomer graft copolymerized to said rubber component.
According to the invention (the sixteenth invention according to claim 16) of a method for recycling the resin mold in accordance with claims 1 to 15 wherein said thermoplastic resin which is the main component of said resin mold is a polymer alloy in which a rubber-like material is combined.
According to the invention (the seventeenth invention according to claim 17) of a method for recycling the resin mold in accordance with claim 16 wherein said rubber-like material is ethylene-propylene-terpolymer or acrylic rubber having good thermal stability.
According to the invention (the eighteenth invention according to claim 18) of a method for recycling the resin mold in accordance with claims 1 to 17 wherein said rubber-like material is pelletized and added in said thermoplastic resin which is shattered and pelletized.
According to the invention (the nineteenth invention according to claim 19) of a method for recycling the resin mold in accordance with claims 1 to 17 wherein said rubber-like material is pelletized and added in said thermoplastic resin which is shattered.